Recently I realized that vSphere 6.0 added one additional option for vSphere On-disk Metadata Analyzer(VOMA) - possibility to fix errors. 
VOMA is a tool (introduced in vSphere 5.1) to check metadata consistency of a file system (such as VMFS) or a logical volume backing the file system. The tool can be useful for the following occurs:
- No access to files located on a VMFS.
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Metadata errors in the vmkernel.log file - e.g:
WARNING: Swap: vm 1086: 3586: Failed to initialize swap file '/volumes/4232e323-faa54323-6f45-001a530a2342/mule/mule-650e6040.vswp': Invalid metadata
- Rebuilt RAIDand disk replacement.
- SAN outage.
Before using VOMA, we need to be sure that:
- All virtual machines on the affected datastore are powered off or migrated to another datastore.
- For VMFS-5 datastores, the datastore needs to unmounted on all ESXi hosts. If you do not do it, you get a similar error:
- Datastore can not be built from multi extents.
In this post I will show how to use this tool to check metadata consistency of VMFS:
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At first we need to obtain the name and partition number of the device that backs the VMFS datastore by:
esxcfg-scsidevs --vmfs
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Run voma with the following options (you have to provide a partition number):
voma -m vmfs -f check -d /vmfs/devices/disks/naa.xxx:y
- If any errors are found, you should open a support case.
Note: In spite of possibility to use fix option, I recommend to consult VMware support before running VOMA with this option. For the latest information, please follow KB: 2036767